Fluid-solid contacting systems have evolved over the years from simple batch operations to more advanced systems that attempt to simulate counter-current continuous flow operations sometimes termed “simulated moving beds” (SMB) in chromatographic separations or “continuous contactors” in ion exchange or adsorption type processes. These SMB systems or continuous contactors only simulate movement of a solid counter current to a fluid since they do not truly and continuously move the solid through the fluid. In essence, any of these systems can be generally termed “Simulated Moving Beds”. This simulation is typically achieved by stepping or indexing a plurality of smaller batch fluid-solid contacting chambers through the various fluid streams by employing multiple numbers of individual valves, single rotary valves, multiple chambers sometimes arranged or combined to simplify the piping, and in some cases rotating tables for the chambers. These systems offer improved process efficiencies over simple batch systems and approach the ideal of truly continuous counter current operation, yet each of the current systems suffer from some deficiency like relatively large capital expense, mechanical complexity, severe process limitation and inflexibility.
An early SMB system design shown in U.S. Pat. No. 3,192,954 to Gerhold featured a single multi compartment tank and a single multiport valve employed in the separation of various non-ionic hydrocarbons. The cost and complexity of the multiport valve and multi compartment tank hampered its acceptance in many applications and spawned simpler designs.
Achieving the same process separation by a less costly manner, many current SMB systems used in chromatography applications employ multiple fluid-solid contacting chambers with multiple valves. See, for example, U.S. Pat. No. 5,705,061 to Moran or U.S. Pat. No. 6,409,922 to Kaneko, which disclose a plurality of valves and a plurality of inlet and outlet pipes from a plurality of chambers. A programmable controller is used to sequence the valves and thereby the flows to the chambers to effect the purification or separation.
To address the sheer number of valves in these designs, a relatively simple multiport rotary valve design was put forth by Ahlgren in U.S. Pat. No. 6,719,001, which was similar in function to earlier U.S. Pat. No. 3,192,954 and suitable for relatively simple chromatographic applications. However, as process conditions become more complex as they do in ion exchange and adsorption type processes, the number of chambers, pipes and programming quickly becomes unmanageable, even with this simplified valve disclosed in the '001 patent.
Therefore, with either individual valves or multiport rotary valves, these SMB system designs are typically used in simple chromatographic separations and not in more complex processes like ion exchange. Generally, these designs are simple, but lack process flexibility.
To address the issue of limited applicability of the aforementioned systems, various “continuous contactor” equipment designs have been put forth to address the complexity of the piping that ensues in more complex purification and separation applications. One widely employed design (See, Rossiter, U.S. Pat. No. 5,676,826) is a single distribution valve for multiple inlets and outlets communicating with fluid-solid contacting chambers mounted on a rotating table. The single distribution valve has a rotating head that moves or indexes in concert with a plurality of fluid-solid contacting chambers on the turntable. As the fluid distribution rotating head and turntable move, the fluid-solid contacting chambers sequentially come into communication with each stationary head inlet and outlet fluid stream. The step time or dwell time of the chambers in contact with the particular fluid streams can be adjusted as dictated by the process. This design affords process flexibility and elegance since the stationary piping separate from the distribution valve determines the process and not the distribution valve, but the design oftentimes suffers from cost and mechanical complexities due to moving extreme weights and hazardous chemicals in chambers on a turntable.
Two more recent designs (U.S. Pat. No. 6,802,970 issued to Rochette and U.S. Patent Application No. 2006/0124177 A1 applied for by Jensen) build upon earlier ideas (U.S. Pat. No. 2,706,532 issued to Ringo, U.S. Pat. No. 4,625,763 issued to Schick and U.S. Pat. No. 5,478,475 issued to Morita) and address the real and perceived mechanical rotation issues by removing the turntable and replacing it with a more complex rotary valve. Both designs accomplish this feat by employing a valve apparatus that has both stationary and rotating parts, which include a number of circular channels and conduits for each inlet and outlet process stream. These circular channels in turn communicate through a rotatable part with the appropriate ports connected to stationary fluid-solid contacting chambers. As the rotating parts are moved or indexed, the next chamber in the sequence is brought into communication with the previous fluid stream. All of the other inlet and outlet fluid streams also follow along in sequence thereby effecting the simulated movement of chambers containing the solid through the fluids. These designs sacrifice process elegance and flexibility but do eliminate the physical movement of the solid fluid chambers on a turntable. They introduce severe deficiency of design in that the process configuration is set by the rotating and stationary part designs and not easily changed at reasonable cost. Consequently, they lack flexibility in application to other processes. For example, an apparatus of one of these designs used in water softening ion exchange could not easily be used for sugar syrup ion exchange or chromatography without major change to the apparatus. These designs also suffer from severe sealing challenges due to the complex nature of sealing a variety of ports, circular channels and faces on various planes and through a wide variety of temperature ranges. As these parts age, the sealing issues can also become more pronounced and again increase maintenance and cost.
Therefore, there is not found in the prior art a rotary valve for simultaneously directing a plurality of fluid streams into or out of fluid-solid contacting chambers suitable for a wide range of processes without one or more of the deficiencies referenced above such as large and potentially dangerous moving turntables, multiple individual valves, complex construction, difficult sealing designs, complex surfaces and limited process flexibility. None of the valves in the prior art recognize that configuration of the stationary connections to the rotary distribution valve are key to complete process flexibility but at the same time eliminating the rotation of chambers on a turntable.